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Nervous system (Instro.)
Picture from http://en.wikipedia.org/wiki/Neuron
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Nervous System
Two types of cells in nervous tissue:
Neurons and Supporting cells
(glial cells in CNS)
Central nervous system (CNS)
= brain and spinal cord
Peripheral nervous system (PNS)
= cranial and spinal nerves
(all nervous tissue outside the CNS)
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Cranial nerve (PNS)
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A
B C
H
F(Pink) G
D
E
A:Dendrites B:Nucleus C: Axon hillcock D:Cell body E:Axon
F(Pink):Myelin H: Schwann cell G: Axon terminal
D:Cell body
__________
__________
A:Dendrites
C:__________
Axon hillcock
__________
E:Axon
F(Pink):Myelin
__________
H:Schwann cell
Nutritional center; nucleus and organelles.
transmit electrical impulses to the cell body.
nerve impulses originate there.
transmits impulse away from the cell body.
is wrapped around the axon
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In periphery, myelin is produced by
Schwann cells.
In CNS, it is produced by oligodendrocytes.
Schwann cells and oligodendrocytes are
Supporting cells.
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A
How many type of cells are seen?Two: Neuron, Schwann cell
What is the unmyelinated part A? Node of Ranvier
What does myelin do? Advantage? Electrically insulates axon.
;improves the conduction
speed of nerve impulses,
enabling fast reactions
Myelinated axons conduct nervous impulses more rapidly than
unmyelinated.
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Structural Classes of Neurons
Pseudounipolar
_______________
-One process
-Dendrites act as receptors
-Axon leads to brain or
spinal cord
-e.g. Most sensory neurons
Bipolar
_______________
-Dendrites and axon arise
from apposite ends of cell
body.
-e.g. Retina
Multipolar
_______________
-Dendrites and axon arise from
apposite ends of cell body.
-e.g. Motor neuron, Interneuron
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Function of Nervous system
1) Senses _______
(such as sight, touch,
stimuli
taste, etc.)
2) Formulates a response to the stimuli
: perceptions, thoughts, and reflexes
CNS
 usually in the ______.
3) Transmits signals rapidly between body parts
:Sense organs  CNS
:CNS  the muscles (Response)
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What are the two supporting cells (glial cells) in the
PNS? What they do?
Schwann cells
______________
-form myelin sheaths around peripheral axons
Satellite cells
______________
-supply nutrients, some structural
function.
-act as protective, cushioning cells.
-lining the exterior surface of neurons;
-surround neuron cell bodies within
ganglia
* Ganglia = collection of cell bodies.
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What are the four supporting cells in the
CNS?
Astrocyte, Ependymal cells,
Oligodendrocyte, & Microglia
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In the CNS
A
E
B
F
C
Fluid!
D
G
A: Capillary B: Astrocyte
D: Cerebral spinal fluid
F: Oligodendrocyte
C: Ependymal cells
E: Neurons
G: Microglia
What are B, C, F, and G? Supporting(glial) cells
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A: Capillary B: Astrocyte
D: Cerebral spinal fluid
F: Oligodendrocyte
C: Ependymal cells
E: Neurons
G: Microglia
All but not A & E
______________are
glial cell in CNS
B: Astrocyte
______________are
common glial cell in CNS
B: Astrocyte
______________form
blood-brain barrier
B: Astrocyte
______________Help
with ion uptake and help move
glucose from blood to brain.
C:
Ependymal cells
______________Neural
stem cells.
G:
Microglia
______________Immune
response in NS, recognizing
infectious agents
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In CNS, Some have myelinated part.
Other have unmyelinated part.
White matter (myelinated part)
Gray matter (unmyelinated part)
(Cell bodies and dendrites are gray
matter)
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________________
Blood-Brain Barrier
-Capillary specializations in the brain
-Do not allowed most nutrients and other molecules in the blood to exit.
astrocytes help with ion uptake and help move glucose from blood to
- But, __________
brain and form blood-brain barrier
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___________
Interneuron
located entirely within CNS, integrates functions in
CNS Sensory (from sensory receptor to CNS)
What are the two types of motor neuron?
Somatic stimulates skeletal muscles
_________
Autonomic affects smooth and cardiac muscle, also glandular
_________
secretion.
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Nerve
___________
Ganglion
___________
___________
Nucleus
Tract
___________
bundle of axons
bundle of nerve cell bodies outside of CNS
bundle of nerve cell bodies within CNS
connects regions of CNS
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neurons, Interneuron, & motor neuron
There are three neuron types Sensory
_____________________________________
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Interneurons
-association neurons
-(PNS/CNS) neuron
CNS
Sensory neurons
-afferent neurons(to the CNS)
-(PNS/CNS) neuron
-to neurons in the CNS
-stimulated by ___________.
sense stimuli
Motor neurons
-efferent neurons (from the CNS)
-(PNS/CNS) neuron
-to muscles or glands
-stimulated by ___________.
interneurons
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______
Nerve
-Bundle of axons in the PNS
-Wrapped by _______________.
connective tissue
-Most mixed nerves: ______________________.
sensory and motor neurons
Cranial
nerves
________________
-Nerves that connect to the CNS in the
head
-(PNS/CNS)
________________
Spinal nerves
-Nerves that connect to the CNS in the spine
-(PNS/CNS)
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Cell membrane is more pearmeable
( K+ than Na+ / Na+ than K+) .
_________________
Equilibrium potential voltage across
membrane due to only 1 ion where
electrical and diffusion forces are
equal and opposite.
ie/ K+ =_______
-90mV , Na+ = _____
60mV
Resting
membrane potential (RMP)
________________________
-Not producing impulses,
-Around _______
-70mV
-K+ drives most of RMP because it is
quite permeable.
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Choose K+, Na+, Cl-, Mg2+
K+ is very permeable and is high inside cell. The inside cell
___
is large (negatively/positively) charged molecules inside the
cell. ___
N+ moves out faster than ___
K+ moves in.
What is the protein transport on the membrane contributes
to the resting membrane potential?Na+/K+ pump
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_______________
Action
potential
-The electrical nerve signal that travels through the axon.
-” ALL or NONE!”
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Voltage-gated sodium channels are found all along the axon.
Potassium channels are found near each voltage-gated sodium
channel.
Threshold voltage
-The voltage enough to open the VGchannel
-50 ~55mv
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1)Resting membrane
2) Membrane potential reaches at threshold.
3) Na+-VG channel open
4) Na+-VG channel close
5) K+-VG channel open
6) K+-VG channel close
7) Na+/K+ pump restore balance of the ions.
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Define “resting membrane potential.” How
many mV is it?
A potential difference across the
membrane. -70mV
*Choose Depolarization, Repolarization, &
Hyperpolarization.
___________ back to the resting potential
Repolarization
___________ positive charges to flow into
Depolarization
the cell.
Depolarization
___________ potential difference approaches zero
Hyperpolarization
___________ potential difference increases by negative
charges enter cell
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*Choose depolarization, repolarization, & hyperpolarization, threshold, K+, Na+.
Na+
The resting cell is more permeable to K+
__ than __.
The leakage channels for K+ are always (open/closed) at the
resting cell.
There are VG channels for K+ and Na+, which are always
(open/closed) at resting cell.
threshold by depolarization
At ________
________, VG channels forNa+
__ are open and
membrane becomes permeable toNa+
__, and Na+
__ can diffuse into
cell causing depolarization
_________.(positive feedback)
;causes a rapid change in MP from –70 to +30 mV
*VG:Votage-gated
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*Choose depolarization, repolarization, & hyperpolarization, threshold, K+, Na+.
Just before VG channels for Na+, VG channels for__
K+,are
open and K+,
__ diffuses out of the cell causing __________,
repolarization
which repolarizes axon back to the resting membrane
potential.
How does the cell return back to the resting membrane potential?
Na/K pumps restore balance of the ions.
*VG:Votage-gated
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Action potential
The electrical nerve signal that travels through the axon.
Action potention is formed by rapid depolarization of the
membrane by (Na+/K+/Mg2+) (influx/efflux); followed by rapid
repolarization by (Na+/K+/Mg2+) (influx/efflux).
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Refractory
period
______________
When a region of the axon has started to depolarize, it must fully
complete its entire depolarization sequence before a new action
potential can begin
refractory period
 called the _______________.
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Review for de-, re-,and Hyperpolarization
K+
Na+
Na+
K+
Resting membrane
Depolarization
Hyperpolarization, but
In action potential, repolarization
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Hyperpolarization
Strength effect = Action
____________
potential frequency
Stronger stimuli stimulate more and more _______.
Axons
As more action potentials are stimulated,
their amplitude (increases/decreases/does not change).
Increased stimulus intensity causes (more/less) APs to be fired.
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Ligand-Receptor interaction
-interaction between a molecule (ligand)
and a protein on or within a target cell
(receptor).
Ligands
~ Neurotransmitter, hormones…
Receptors
~ Neurotransmitter receptors, hormone
receptors, ligand-gated channel… (specific!)
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__________is
a connection between a
Synapse
neuron, called __________,
presynaptic and an another
cell, called __________.
postsynaptic
There are a few _________
electrical synapse in
nervous system, in smooth muscle and in
heart gap junctions.
Most are __________
chemical synapses.
Synaptic transmission at chemical synapses is via
_______________.
neurotransmitters
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A : Neuron (Presynaptic)
B : Neuron or cells (Postsynaptic)
C: Neurotransmitter(NT)
C
1. Mitochondria 2. Synaptic vesicle
3. Autoreceptor 4. Synaptic cleft
5. NT receptor
6. Calcium Channel
7. release NT by___________
exocytosis
8. NT re-uptake pump
Chemical Synapse!
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Synaptic
Transmission
1.Action potentials reach
at the axon terminal.
2.VG-Ca2+ channels
open.
3. Ca2+ activates calmodulin.
4. Calmodulin activates a
protein kinase.
5. Protein kinase promote
fusion and exocytosis of
vesicles.
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Depolarizing channels cause
___________________________
EPSPs
(excitatory postsynaptic potentials)
Hyperpolarizing channels cause
__________
IPSPs
(inhibitory postsynaptic potentials)
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EPSPs and IPSPs summate.
 if membrane potential in postsynaptic cell reaches
threshold at the axon hillock, a new AP is generated.
 if not, no AP occur.
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Acetylcholine (ACh) is most widely used as ______
NT
and
has _________
nicotinic and ___________
muscarinic receptor.
________________
nicotinic
muscarinic
________________
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Nicotinic ACh Receptor
Muscarinic ACh Receptor
Where are they?
Where do they do?
Some glands
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